About 8 million people die of cancer each year according to the World Health Organization. Cancer is the uncontrolled growth of cells and can lead to malignant tumors that resist treatment, spread through the body, and potentially recur after removal. Early detection and vigilant monitoring are key to minimizing cancer's harm.
A lump in a patient may be biopsied to determine if it is a malignant tumor, but this only occurs after the lump has appeared. Some tumors, such as lung tumors, require difficult and painful biopsies in which a fine needle is inserted to the site of the tumor. A minimally-invasive procedure known as “liquid biopsy”, which involves sequencing DNA from a patient's blood, promises to provide early detection.
Unfortunately, there are limits to the insights offered by a liquid biopsy. Sequence reads are generally analyzed by mapping them to a reference genome. Any difference between a sequence read and the reference is called as a mutation in the patient without regard to which should be considered the healthy genotype. The physician is left to search the literature to interpret the mutations found in the patient.